Articles are often formed by injecting heated fluid into a mold. The fluid is introduced into a runner in a nozzle body. The fluid then flows through a gate into a hollow cavity in the mold. The fluid is heated as it flows through the runner in the nozzle body. When the fluid has solidified in the hollow cavity in the mold, it is sheared at the position where the fluid flows through the gate into the mold cavity.
Articles have been formed for decades, if not for centuries, by injecting fluid into hollow cavities in molds. In all of this period of time, certain problems have continued to exist in spite of considerable efforts during this period to resolve such problems. For example, when articles have been formed in a first color (e.g. blue) and articles are then desired to be formed in a second color (e.g. red) different from the first color, it has been difficult to rid the nozzle runner and the gate of any fluid of the first color. As will be appreciated, it is important to rid the nozzle body of any fluid of the first color so that this fluid will not taint the fluid of the second color as the fluid of the second color flows through the nozzle runner.
In order to cleanse the nozzle runner of the first color, fluid of the second color has had to be passed through the nozzle body for an extended period of time extended period of time, any articles formed have not been able to be used since the color of such articles has been a mixture of the first and second colors. Furthermore, the color of the mixture is not predictable at any instant during the initial period after the fluid of the second color has been substituted for the fluid of the first color. This has represented a considerable waste of fluid. It has also represented a considerable period of time in which the nozzle and the molds cannot be gainfully used.